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Asked: 2026-05-21T18:30:53+00:00

<?php $filename=vast/Vastopolis_Map.png; $image = imagecreatefrompng($filename); // get properties of the image as an array

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<?php
$filename="vast/Vastopolis_Map.png";
$image = imagecreatefrompng($filename);

// get properties of the image as an array $size
// $size[0] is the width of the image in pixel
// $size[1] is the height

$size = getimagesize($filename);
$width = $size[0];
$height = $size[1];

// Set the color (red)
$ink_color = imagecolorallocatealpha ($image, 244, 1, 1, 100);
// Set line thickness if needed
// imagesetthickness($image, 5);

// get GPS locations where text meets selection criteria
// Connect to MySQL, assume the database is called vast
$dsn = 'mysql:host=localhost;dbname=vast';
$username = '###';
$passwd = '###';

$db = new PDO($dsn, $username, $passwd);

// Select text that mentions flu or fever
// Option 1: text like '%flu%' or text like '%fever%'
// Option 2: text regexp 'flu|fever'
$sql = "SELECT Location, Text FROM blogs WHERE Text LIKE '%flu%' '";
$results = $db->query($sql);

// Linear transformation to match the coordinates on the map
// The upper left corner of the map: 42.3017, 93.5673
// The lower right corner of the map: 42.1609, 93.1923
$minX = 42.3017;
$maxX = 42.1609;

$minY = 93.5673;
$maxY = 93.1923;
// Linear transformation. What does it do?
$a = $width/($maxX-$minX);
$b = -$minX*$a;

$c = $height/($maxY-$minY);
$d = -$minY*$c;

// Set the color of the markers - red
$color = imagecolorallocatealpha ($image, 250, 10, 10, 50);

// plot each location returned from the query to the database
foreach ($results as $row) {
$location = $row[0];
$pos = preg_split("/\s+/", $location); // why?
$X = $pos[0];
$Y = $pos[1];
$x = $a*$X + $b;
$y = $c*$Y + $d;
imagefilledellipse($image, $x, $y, 10, 10, $color);
}
// serve the image to the client
header ("Content-type: image/png");
imagepng($image);
imagedestroy($image);

?>

it is throwing this disgusting error, anyone??

Warning: Invalid argument supplied for foreach() on line 51

Warning: Cannot modify header information - headers already sent by  on line 61
‰PNG  IHDR` ]×ý{~÷PLTEôú ûûûèæÙãÒìæÓÔÖçæËäÎÑÐêÒÐÑæï®âæšìέéšÈê³ØâšËÔ¯ËËä¼åæ·ËзæˬÏÃÆ殭㸑ä æŽÏ®¯Ð­‰Ç—¬Æ‘Œºãó»ãÒ·Èí±ÒÆË÷˜Èù䫷⚮̭ªÌ‘›Â±šÄŠ¨Ï­­®­²®‹®°Œ’´§¬Ž’§‹‹ÄÅyä­yæ€}ò‘IÌ¥yõYĘpÃ[ùƒ+Ê8®Â{¬¬m¤¥Z±i®„X‰¬q™¢Y‹“nŽP¨¢;¤‚<‘ >„ˆ;„å}Är¦É}ƒ{ͤ|¤§v¦\¡©VŒ–v¤mX¨…\…‘2‡çppð`^ç\bêPQÔpqÊnVÒ]bÔQRíy%þjë@>ìZÌr'ÒiØA>ÍX ð=CÔ>Bë34ñ!þ"ý   Õ67Å:̧rn¥yQ¢\f«RSnm‘mLŠYo†YL£v;´e«\+±XŽf:ƒm†Y5ŒT®=F†2m„:L‚m­/1®'¾‰2+‚'Ž ƒ rÀúT¤ázª¤|¢{ˆ¢s“‰P¥¥U¨‰O‡¯[ˆƒ“þ-ƒ¸-‘¶……z£ix¡[qllŽT[¡n_ C[ƒrZ…Lxƒ:iƒU…:Sƒ2‡m4„W‚w…N2ƒg`Õsk³qsˆdZ´tU†Jx©[iƒUK±UMŽC;Ùj0‡d‡E9¬H8\ {È&mŸ$á3)®3'—&®&”­‘mmpltPmRnqQNVpmToLSUkOONqn6~jrO0kHNm5Z}NT0NNfde:.f:p#~R4/N0L-C8kf-lG8Kf4PN~~lDJ~GH*g7&~2R-/Md8sU-G63c25M#}5Jtéã°ER¶ÁSÆ3tŸwC×ëx<ñ“ÏɼøÇvæßžpvü0#V>¶[û]oGÿÏÓc{ÚhEõlóï‡1g çFû|‡Úà®–\¿^o×ö~mÏãO?ÿô`Åè^<ë®òe{öØÓ>°ý~ק íøszŠè꾪nz¤>â<äø°^÷:̶óu;ö]…:þtÜöUÍ’«6QvKn|@ÉÖL¸ëoêk8|`ítSû9«°\Ú³Ï'BÆ•¥5ڪ㎨_tû «¬tøíúív½¶;ÿÝow>»À›íÃÃÑÊÓuµýò𪪶Gœ€Õvª?”è”;Ee§`þm{az`Ÿ­åzÄyí1"‹žÝÑÎ÷ÓqTÓXÕvÖKí÷

Not sure if this is a db error, or something with php. Completely lost why its doing this or what its talking about.

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1 Answer

  1. Editorial Team

    You have an stray ‘ in your query, which makes it invalid

    $sql = "SELECT Location, Text FROM blogs WHERE Text LIKE '%flu%' '";

    should be

    $sql = "SELECT Location, Text FROM blogs WHERE Text LIKE '%flu%'";

    A malformed query will make $results an error code instead of an array of results. Since there are no results in $results, you can’t use foreach on it without errors, as foreach can only be used on arrays.

    Since the foreach causes an error, which prints and send to the user, it will generate the “headers already sent” error. Which the cause, and the effect will be solved too.

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